Catalyst for producing alpha, beta-unsaturated carboxylic acid and method for preparation thereof, and method for producing alpha, beta-unsaturated carboxylic acid

ABSTRACT

The object of the present invention is to provide a catalyst which can produce an α,β-unsaturated carboxylic acid through liquid-phase oxidation of an olefin or an α,β-unsaturated aldehyde in good reaction performance, a method for producing the catalyst, and a method for producing an α,β-unsaturated carboxylic acid by using the catalyst. The present invention resides in a catalyst for producing an α,β-unsaturated carboxylic acid, wherein a metal is supported on a carrier with a total pore volume of 0.40 to 1.50 cc/g as measured by nitrogen gas adsorption method, or wherein palladium with an average particle diameter in the range of 1 to 8 nm is supported on the carrier.

TECHNICAL FIELD

The present invention relates to a catalyst for producing anα,β-unsaturated carboxylic acid through liquid-phase oxidation of anolefin or an α,β-unsaturated aldehyde, a method for producing thecatalyst and a method for producing an α,β-unsaturated carboxylic acidby using the catalyst.

BACKGROUND ART

Many of α,β-unsaturated carboxylic acids are industrially useful. Forexample, acrylic acid or methacrylic acid is being used in aconsiderable amount for the application such as a raw material ofsynthetic resins. Although examples include gas-phase oxidation andliquid-phase oxidation of isobutene and a method by way of acetonecyanohydrin as a method for producing methacrylic acid, there is not aspecifically advantageous method and methacrylic acid has beenindustrially produced by these several methods.

There has been many researches on a catalyst and a method for producingan α,β-unsaturated carboxylic acid through liquid-phase oxidation of anolefin or an α,β-unsaturated aldehyde with molecular oxygen. Examplesinclude a method in the presence of gold supported catalyst (PatentDocument 1), a method using a palladium metal catalyst (Patent Documents2 to 6) and a method using a molybdenum compound and a palladiumcatalyst (Patent Document 7).

The catalysts disclosed in Patent Documents 2 to 7 contain palladium asa component of a catalyst, however, there is no description concerningparticle diameter of palladium. Further, some of the catalysts disclosedin Patent Documents 1 to 7 are supported on a carrier such as activatedcarbon, alumina or silica. However, as for physical properties of thesecarriers, there is merely one description in Patent Document 1 as “it ispreferable to use a hydrophobic carrier or a conventional carriersubjected to hydrophobic treatment”, and there are no otherdescriptions, in those documents, referring to physical properties ofthese carriers.

-   Patent Document 1: Japanese Patent Application Laid-Open No.    2001-172,222.-   Patent Document 2: Japanese Patent Application Laid-Open No.    60-155,148.-   Patent Document 3: Japanese Patent Application Laid-Open No.    60-139,341.-   Patent Document 4: Japanese Patent Application Laid-Open No.    60-139,643.-   Patent Document 5: U.S. Pat. No. 4,435,598.-   Patent Document 6: International Publication No. WO 02/083,299.-   Patent Document 7: Japanese Patent Application Laid-Open No.    56-59,722.

DISCLOSURE OF INVENTION Problem to be Solved by the Invention

When the present inventors produced acrylic acid from propylene by usingthe catalyst produced according to the methods of Examples described inPatent Documents 1 to 7, it was found that by-products such as variouspolymers and oligomers were produced in large amount in addition to theby-products described in Patent Documents 1 to 7 (for example,acetaldehyde, acetone, acrolein, acetic acid and carbon dioxide). InPatent Documents 1 to 7, these polymers and oligomers were not captured,and hence, the actual selectivity to acrylic acid and the yield ofacrylic acid in view of these by-products were found to be lower thanthose described in Examples of Patent Documents 1 to 7. Consequently,the reaction performance obtained in the method for producing anα,β-unsaturated carboxylic acid in Patent Documents 1 to 7 was notsufficient yet, and hence, further improvement on this point has beendesired.

The object of the present invention is to provide a catalyst which canproduce an α,β-unsaturated carboxylic acid through liquid-phaseoxidation of an olefin or an α,β-unsaturated aldehyde in good reactionperformance, a method for producing the catalyst and a method forproducing an α,β-unsaturated carboxylic acid by using the catalyst.

Means for Solving Problem

The present inventors have found that the catalyst performance isconsiderably influenced by physical properties of a carrier to be usedin producing a catalyst, in particular, by pore volume, and thus havecompleted the present invention. The present inventors have also foundthat, when palladium is used as a component of a catalyst, the catalystperformance is considerably influenced by a particle diameter ofpalladium in the catalyst produced, and thus have completed the presentinvention.

A catalyst for producing an α,β-unsaturated carboxylic acid of thepresent invention is a catalyst for producing an α,β-unsaturatedcarboxylic acid through liquid-phase oxidation of an olefin or anα,β-unsaturated aldehyde and is the following:

-   (i) A catalyst for producing an α,β-unsaturated carboxylic acid,    wherein a metal is supported on a carrier with a total pore volume    of 0.40 to 1.50 cc/g as measured by nitrogen gas adsorption method;    or (ii) A catalyst for producing an α,β-unsaturated carboxylic acid,    wherein palladium with an average particle diameter in the range of    1 to 8 nm is supported on a carrier.

A method for producing the catalyst for producing an α,β-unsaturatedcarboxylic acid of the present invention is a method for producing thecatalyst for producing an α,β-unsaturated carboxylic acid of the above(i), wherein a metal compound is reduced by a reducing agent in thepresence of the above carrier.

A method for producing the catalyst for producing an α,β-unsaturatedcarboxylic acid of the present invention is a method for producing thecatalyst for producing an α,β-unsaturated carboxylic acid of the above(ii), wherein a palladium compound is reduced by a reducing agent in thepresence of the above carrier.

A method for producing an α,β-unsaturated carboxylic acid of the presentinvention is a method for producing an α,β-unsaturated carboxylic acidthrough liquid-phase oxidation of an olefin or an α,β-unsaturatedaldehyde with molecular oxygen in the presence of the catalyst forproducing an α,β-unsaturated carboxylic acid of the above (i) or (ii).

Effect of the Invention

According to the present invention, a catalyst which can produce anα,β-unsaturated carboxylic acid through liquid-phase oxidation of anolefin or an α,β-unsaturated aldehyde in good reaction performance, amethod for producing the catalyst and a method for producing anα,β-unsaturated carboxylic acid by using the catalyst can be provided.

BEST MODE FOR CARRYING OUT THE INVENTION

(1) Catalyst for Producing an α,β-Unsaturated Carboxylic Acid

The catalyst for producing an α,β-unsaturated carboxylic acid of thepresent invention (hereinafter, sometimes expressed as “catalyst”) is acatalyst for producing an α,β-unsaturated carboxylic acid throughliquid-phase oxidation of an olefin or an α,β-unsaturated aldehyde andis the following:

-   (i) A catalyst for producing an α,β-unsaturated carboxylic acid,    wherein a metal is supported on a carrier with a total pore volume    of 0.40 to 1.50 cc/g as measured by nitrogen gas adsorption method;    or-   (ii) A catalyst for producing an α,β-unsaturated carboxylic acid,    wherein palladium with an average particle diameter in the range of    1 to 8 nm is supported on a carrier.

By using the above-mentioned catalyst, an α,β-unsaturated carboxylicacid can be produced through liquid-phase oxidation of an olefin or anα,βunsaturated aldehyde in good reaction performance. The catalyst ofthe present invention is especially effective for liquid-phase oxidationof propylene and isobutylene among olefins and liquid-phase oxidation ofacrolein and methacrolein among α,β-unsaturated aldehydes.

The catalyst of the present invention is a supported catalyst in which ametal is supported on a carrier. Hereinafter, a carrier and a metal,which can be used as the catalyst of the present invention, will beexplained.

(1-1) Carrier

The kind of the carrier of the present invention is not particularlylimited and typical carriers such as activated carbon, carbon black,silica, alumina, magnesia, calcia, zirconia and titania can be used.Among them, activated carbon or silica is preferably used. Activatedcarbon is generally produced through the processes of carbonization,granulation, activation, washing, drying and pulverization, and theseproducing processes are not particularly limited in the presentinvention. A carbonaceous material which is the raw material ofactivated carbon is not particularly limited either, and various rawmaterials such as coconut shell, coal, lignin and synthetic resin can beused. The process of activation is not particularly limited either, andwater vapor, carbon dioxide, oxygen, phosphoric acid, phosphate and zincchloride can be used for activation. The activated carbon after theactivation process is washed with mineral acid, hydrochloric acid andwater, if necessary, and dried to be put to use. Among impuritiescontained in the product activated carbon, it is preferable to keep theamount of chlorine as small as possible because chlorine sometimescauses bad effects on the catalyst performance. Therefore, an activatedcarbon produced by using zinc chloride or hydrochloric acid ispreferably washed sufficiently to remove the contained chlorine. Theshape of the activated carbon is not particularly limited either and theactivated carbon having various shapes such as powder, sphere, pelletand fiber can be used. The BET specific surface area of the activatedcarbon is preferably 300 m²/g or more, particularly preferably 600 m²/gor more, and preferably 4,000 m²/g or less, particularly preferably2,500 m²/g or less.

One embodiment of the catalyst of the present invention is to select anduse a carrier with a total pore volume of 0.40 to 1.50 cc/g as measuredby nitrogen gas adsorption method. By using such a carrier, anα,β-unsaturated carboxylic acid can be produced through liquid-phaseoxidation of an olefin or an α,β-unsaturated aldehyde in highselectivity and high productivity. Hereinafter, the constitution of theabove carrier and the method for producing the carrier will beexplained.

In particular, to obtain a target product in high selectivity, it ispreferable to select a carrier with a total pore volume of 0.40 to 0.80cc/g. The total pore volume is more preferably 0.47 cc/g or more,further preferably 0.70 cc/g or less, and furthermore preferably 0.67cc/g or less. By using a carrier which fulfills such requirements, atarget product such as acrylic acid or methacrylic acid can be obtainedin good selectivity with little formation of by-products. Theselectivity of the target product is improved because selecting asmaller range within the aforementioned range of the total pore volumeis supposed to suppress the formation of by-products such as oligomers.Further, in this case, a proportion of the pore volume of the mesoporehaving a pore size of from 2 nm through 50 nm to the total pore volumeis preferably 40% or less to the total pore volume, more preferably 35%or less, furthermore preferably 30% or less and particularly preferably20% or less. Further, the above proportion of the pore volume of themesopore is preferably 5% or more to the total pore volume, morepreferably 7% or more and furthermore preferably 9% or more. In thiscase, in particular, when the total pore volume are the same, thecarrier with lower proportion of the mesopore is supposed to have thetendency to form lesser amount of by-products such as oligomers, andhence, improves the selectivity. Further, the BET specific surface areaof the carrier is preferably 600 m²/g or more, more preferably 800 m²/gor more, and preferably 2,000 m²/g or less, more preferably 1,500 m²/gor less.

In particular, to obtain a target product in high productivity, it ispreferable to select the carrier with a total pore volume of 0.70 to1.50 cc/g. The total pore volume is more preferably 0.80 cc/g or more,furthermore preferably 0.90 cc/g or more, and more preferably 1.40 cc/gor less, furthermore preferably 1.30 cc/g or less. By using a carrierwhich fulfills such requirements, a target product such as acrylic acidor methacrylic acid can be obtained in good productivity with highactivity of the catalyst. The productivity of the target product isimproved because selecting a larger range within the aforementionedrange of the total pore volume is supposed to make internal porediffusion of reactants and products easy. Further, a proportion of thepore volume of the mesopore having a pore size of from 2 nm through 50nm to the total pore volume is preferably 10% or more to the total porevolume, more preferably 20% or more, furthermore preferably 30% or moreand particularly preferably 40% or more. Further, the above proportionis preferably 65% or less, more preferably 60% or less and furthermorepreferably 55% or less. In this case, in particular, when the total porevolumes are the same, the carrier with larger proportion of the mesoporeis supposed to have the tendency to make internal pore diffusion easier,and hence, improves the production efficiency. Further, the BET specificsurface area of the carrier is preferably 100 m²/g or more, morepreferably 300 m²/g or more, and preferably 5,000 m²/g or less, morepreferably 4,000 m²/g or less.

The total pore volume, the pore volume of the mesopore having a poresize of from 2 nm through 50 nm and the BET specific surface area of thecarrier are measured by, for example, Surface Area and PorosimetryAnalyzer, TriStar 3000 (trade name), manufactured by MicromeriticsInstrument Corporation.

(1-2) Metal

The metal to be supported on the carrier is not particularly limited aslong as it functions as a catalyst of liquid-phase oxidation, however,noble metal is preferable, palladium or gold is more preferable andpalladium is particularly preferable. The metal can be used alone or incombination of two or more kinds. Further, the metal may contain anothermetal which does not function as a catalyst of liquid-phase oxidation.The content of the metal which does not function as a catalyst ofliquid-phase oxidation is preferably 50 atomic % or less from theviewpoint of catalyst activity.

One embodiment of the catalyst of the present invention is a catalyst inwhich palladium with an average particle diameter in the range of 1 to 8nm is supported on a carrier. By selecting palladium as a metal andcontrolling its average particle diameter to fall in the range of 1 to 8nm, a catalyst which can produce an α,β-unsaturated carboxylic acid froman α,βunsaturated aldehyde in high yield can be obtained. Theabove-mentioned average particle diameter is preferably 1.2 nm or more,more preferably 1.4 nm or more and preferably 7 nm or less, morepreferably 6 nm or less. When the average particle diameter of palladiumis outside the above range, the activity of the catalyst containing theabove palladium is liable to be lowered, and hence, the yield of anα,β-unsaturated carboxylic acid is liable to be lowered. At this time,the catalyst may contain a metal other than palladium, however, thecontent of the metal other than palladium is preferably 50 atomic % orless from the viewpoint of catalyst activity.

The average particle diameter of palladium mentioned above means a valuemeasured with palladium in the catalyst by transmission electronmicroscope, which is concretely calculated as follows.

Print out an image of transmission electron microscope with the samemagnification as that of the observation, and randomly sample 50 pointsof the palladium regions in the field of view and measure particlediameter of each palladium region; measure the particle diameter byassuming its shape to be circular because the shape of the palladiumregion is almost circular; and carry out these operations with 3 fieldsof view and average the measured values to obtain an average particlediameter.

Here, the observation by transmission electron microscope is carried outwith a magnification under which the measurement of a palladium particlediameter is possible.

The average particle diameter of palladium in the catalyst variesdepending on various conditions such as a kind of carrier and BETspecific surface area of a carrier to be used, a kind of solvent andmixing ratio in the case of mixed solvent to be used in the preparationof the catalyst, a kind and concentration of a palladium compound whichis a raw material of the catalyst, and temperature and time of reducingthe palladium compound. In the present invention, it is necessary tocontrol the average particle diameter of palladium in the catalyst to beobtained to fall in the above-mentioned range by properly selecting andsetting these conditions.

(2) A Method for Producing a Catalyst for Producing an α,β-UnsaturatedCarboxylic Acid

In the next place, a method for producing the above-mentioned catalystfor producing an α,β-unsaturated carboxylic acid of the presentinvention will be explained.

The method for producing the catalyst of the present invention is notparticularly limited, however, it is preferable to select a method inwhich a metal compound is reduced by a reducing agent in the presence ofa carrier. Concretely, the catalyst can be prepared, for example, by aliquid-phase reduction method in which a metal compound solution withdispersed carrier is prepared and a reducing agent is added to it toreduce the metal compound or by a gas-phase reduction method in which acarrier impregnated with a metal compound solution is dried and thensubjected to reduction in a reducing atmosphere. Among them, theliquid-phase reduction method is preferable. Hereinafter, a method forproducing the catalyst by the liquid-phase reduction method will beexplained.

As the metal compound to be used, it is preferably chlorides, oxides,acetates, nitrates, sulfates, tetraammine complex or acetylacetonatocomplex of the metal which becomes the catalyst, more preferablychlorides, oxides, acetates, nitrates or sulfates of the metal,furthermore preferably chlorides, acetates or nitrates of the metal.These compounds can be used alone or in combination of two or morekinds.

Further, as these metal compounds, it is also preferable to use thosewhich do not substantially contain chlorine as an impurity. Moreconcretely, it is preferable that chlorine content in the metal compoundis 1,000 ppm or less. In other words, it is preferable to use metalcompounds which do not contain chlorine such as acetates, nitrates orbisacetylacetonato complexes. When palladium is selected as the metal,for example, palladium acetate, palladium nitrate orbisacetylacetonatopalladium can be suitably used.

As the solvent to dissolve the metal compound; it is properly selectedin view of solubility of the metal compound and the reducing agent anddispersibility of the carrier. Water, alcohols, ketones, organic acids,hydrocarbons or mixed solvent of two or more kinds selected from thesegroups can be used. As the solvent, at least one organic solventselected from the group consisting of alcohols, ketones and organicacids is preferable, and at least one organic solvent selected from thegroup consisting of organic acids having carbon number of 2 to 6,tertiary butanol and ketones having carbon number of 3 to 6 is morepreferable.

It is also preferable to use a mixed solvent of water and an organicsolvent because a catalyst with better performance can be prepared. Whenthe mixed solvent of water and an organic solvent is used, a mixedsolvent of water and at least one organic solvent selected from thegroup consisting of alcohols, ketones and organic acids is preferable.Among them, a mixed solvent of water and at least one organic solventselected from organic acids is more preferable. As the organic acids, atleast one organic acid selected from the group consisting of aceticacid, propionic acid, n-butyric acid, iso-butyric acid, n-valeric acidand iso-valeric acid is preferable. Among them, n-valeric acid or aceticacid is particularly preferable. In this case, the amount of water isnot particularly limited, however, it is preferably 5% by weight or moreto the weight of the mixed solvent, more preferably 8% by weight ormore. In addition, the amount of water mentioned above is preferably 60%by weight or less, more preferably 50% by weight or less, furthermorepreferably 40% by weight or less. In the case of mixed solvent, it ispreferable that the solvent is homogeneous, while it may beheterogeneous.

A carrier and a metal compound are added to the above-mentioned solventin a desired order or simultaneously to prepare a metal compoundsolution with dispersed carrier. Concentration of the metal compound ispreferably 0.1% by weight or more, more preferably 0.2% by weight ormore, particularly preferably 0.5% by weight or more. Besides,concentration of the above metal compound is preferably 20% by weight orless, more preferably 10% by weight or less, furthermore preferably 7%by weight or less and particularly preferably 4% by weight or less.

In the next place, a reducing agent is added to the metal compoundsolution with dispersed carrier to reduce the metal compound, to obtaina catalyst in which the metal is supported on the carrier.

The reducing agent to be used is not particularly limited and anymaterial can be used as long as it has the ability to reduce a metal inits oxidized state in the metal compound. For example, hydrazine,formaldehyde, sodium borohydride, hydrogen, formic acid, formates,alcohols and olefins can be used. Among them, at least one compoundselected from the group consisting of formaldehyde, propylene,isobutylene, 1-butene and 2-butene is preferable and formaldehyde,propylene or isobutylene is more preferable.

When a gas such as propylene is used as the reducing agent, it ispreferable to charge a metal compound solution with dispersed carrier ina pressure device such as autoclave and to pressurize the inside withthe reducing agent to carry out reduction. The pressure is preferably0.1 to 1.0 MPa (gauge pressure; hereinafter, pressure is all expressedin gauge pressure).

When the reducing agent is liquid or solid, reduction can be carried outby adding the reducing agent in a metal compound solution with dispersedcarrier. In this case, the amount of the reducing agent is preferably 1to 50 mols to 1 mol of the metal compound.

Temperature of the system at the time of reduction and reducing time aredifferent depending on a method of reduction, a carrier and a metalcompound to be used, solvent, a reducing agent and the like and cannotbe absolutely said. In the case of liquid-phase reduction method,reducing temperature is preferably -5° C. or higher, more preferably 0°C. or higher, furthermore preferably 15° C. or higher, and preferably150° C. or lower, more preferably 100° C. or lower, furthermorepreferably 80° C. or lower. Reducing time is preferably 0.1 hour ormore, more preferably 0.25 hour or more, furthermore preferably 0.5 houror more, and is preferably 24 hours or less, more preferably 4 hours orless, furthermore preferably 3 hours or less and particularly preferably2 hours or less.

After reduction, a catalyst in which the metal is supported on thecarrier is separated from the dispersion. The method of separation isnot particularly limited and, for example, filtration or centrifugationcan be used. The catalyst thus separated is properly dried. The dryingmethod is not particularly limited and various methods can be used.

Concentration of the metal contained in the residual solution separatedfrom the catalyst after reduction is preferably 10 mg/l or less. Thisamount can be adjusted by concentration of the metal compound beforereduction, a reducing condition or the like. The presence of the metalin the solution can be easily confirmed by adding a reducing agent suchas hydrazine, and the amount of the metal in the solution can bedetermined quantitatively with an elemental analysis such as ICP.

The supported metal rate of the catalyst is preferably 0.1% by weight ormore to the carrier before the metal is supported, more preferably 0.5%by weight or more, furthermore preferably 1% by weight or more andparticularly preferably 4% by weight or more. Besides, the supportedmetal ratio of the catalyst is preferably 40% by weight or less to theweight of the carrier before the metal is supported, more preferably 30%by weight or less, furthermore preferably 20% by weight or less andparticularly preferably 15% by weight or less. The supported ratio canbe obtained from weight of the carrier used in the preparation of thecatalyst, weight of the metal in the metal compound and weight of themetal contained in the residual solution separated from the catalystafter reduction.

The catalyst thus produced may be used for the reaction in the state ofdispersion after washing with a solvent or in the state of isolated formby centrifugation or filtration.

The catalyst may be activated previous to being served to liquid-phaseoxidation. The method for activation is not particularly limited andvarious methods can be used. As the method for activation, a method ofheating under reducing atmosphere in a flow of hydrogen is preferable.

(3) A Method for Producing an α,β-Unsaturated Carboxylic Acid

In the next place, a method for producing an α,β-unsaturated carboxylicacid through liquid-phase oxidation of an olefin or an α,β-unsaturatedaldehyde by using the catalyst for producing an α,β-unsaturatedcarboxylic acid of the present invention thus obtained will beexplained.

Examples of the raw olefin of the liquid-phase oxidation includepropylene, isobutylene and 2-butene. Examples of the raw α,β-unsaturatedaldehyde include acrolein, methacrolein, crotonaldehyde(β-methylacrolein) and cinnarimaielhyde (β-phenylacrolein). The rawolefin or the raw α,β-unsaturated unsaturated aldehyde may contain asmall amount of impurities such as a saturated hydrocarbon and/or asaturated lower aldehyde.

In the case that an olefin is used as the raw material, theα,β-unsaturated carboxylic acid to be produced in the liquid-phaseoxidation has the same carbon skeleton as the original olefin. Further,in the case that an α,β-unsaturated aldehyde is used as the rawmaterial, its aldehyde group changes into carboxyl group in theα,β-unsaturated carboxylic acid to be produced.

The catalyst of the present invention is suitable for producing acrylicacid from propylene or acrolein, or methacrylic acid from isobutylene ormethacrolein through liquid-phase oxidation.

As a source of molecular oxygen to be used in the reaction, air iseconomical, and also pure oxygen or mixed gas of air and pure oxygen canbe used. If necessary, mixed gas in which air or pure oxygen is dilutedwith nitrogen, carbon dioxide, water vapor or the like can be used too.

A solvent to be used in the liquid-phase oxidation reaction is notparticularly limited and, for example, water; alcohols such as tertiarybutanol and cyclohexanol; ketones such as acetone, methyl ethyl ketoneand methyl isobutyl ketone; organic acids such as acetic acid, propionicacid, n-butyric acid, iso-butyric acid, n-valeric acid, iso-valericacid; organic acid esters such as ethyl acetate and methyl propionate;hydrocarbons such as hexane, cyclohexane and toluene; or a mixed solventconsisting of two or more kinds of solvents selected from these groupscan be used. Among them, at least one solvent selected from the groupconsisting of alcohols, ketones, organic acids and organic acid estersis preferable, and at least one solvent selected from the groupconsisting of organic acids having carbon number of 2 to 6, tertiarybutanol and ketones having carbon number of 3 to 6 is more preferable,and a solvent containing any one of tertiary butanol, acetic acid andn-valeric acid is particularly preferable. Further, a mixed solvent ofwater and at least one solvent selected from the group consisting ofalcohols, ketones, organic acids and organic acid esters is preferablebecause the performance of the liquid-phase oxidation is furtherimproved by using this solvent. In this case, the amount of water is notparticularly limited, however, it is preferably 2% by weight or more tothe weight of the mixed solvent, more preferably 5% by weight or more,and preferably 70% by weight or less to the weight of the mixed solvent,more preferably 50% by weight or less. It is desirable that the solventis homogeneous, while it can be used in a heterogeneous state.

Although the liquid-phase oxidation reaction may be carried out eitherin a continuous system or in a batch system, a continuous system ispreferable for industry in view of productivity.

The amount to be used of the raw olefin or the raw α,β-unsaturatedaldehyde is generally 0.1 part by weight or more to 100 parts by weightof the solvent, and preferably 0.5 part by weight or more; and generally20 parts by weight or less, and preferably 10 parts by weight or less.

The amount to be used of the molecular oxygen is preferably 0.1 mol ormore to 1 mol of the raw olefin or the raw α,β-unsaturated aldehyde,more preferably 0.3 mol or more and particularly preferably 0.5 mol ormore. The above amount to be used is preferably 30 mols or less, morepreferably 25 mols or less, furthermore preferably 20 mols or less,particularly preferably 15 mols or less and most preferably 10 mols orless.

The catalyst is generally used in a dispersed state in a reaction liquidin which liquid-phase oxidation is carried out, while it may be used ina fixed bed. The amount of the catalyst to be used is preferably 0.1part by weight or more as the catalyst existing in the reactor to 100parts by weight of solution existing in the reactor, more preferably 0.5part by weight or more, and particularly preferably 1 part by weight ormore. The above amount to be used is preferably 30 parts by weight orless, more preferably 20 parts by weight or less, and particularlypreferably 15 parts by weight or less.

The reaction temperature and the reaction pressure are properly setdepending on the solvent and the raw materials to be used. The reaction-temperature is preferably 30° C. or more, more preferably 50° C. ormore, furthermore preferably 60° C. or more and particularly preferably70° C. or more. The reaction temperature is preferably 200° C. or less,more preferably 150° C. or less. The reaction pressure is preferablyatmospheric pressure (0 MPa) or more, more preferably 0.5 MPa or moreand furthermore preferably 2 MPa or more, and preferably 10 MPa or less,more preferably 7 MPa or less and furthermore preferably 5 MPa or less.

When the reaction is carried out under pressure, it is preferable to usean autoclave having a stirring function.

EXAMPLES

Hereinafter, the present invention is further explained concretely withreference to examples and comparative examples, however, the presentinvention is not limited to those examples. In the following examplesand comparative examples, “part” means part by mass.

(Analysis of a Raw Material and a Product)

Analysis of a raw material and a product was carried out by using gaschromatography. The conversion of an olefin or an α,β-unsaturatedaldehyde; the selectivity to an α,β-unsaturated aldehyde to be produced;the selectivity to a polymer/oligomer to be produced; the selectivity toan α,β-unsaturated carboxylic acid to be produced, and the yield andproductivity of an α,β-unsaturated carboxylic acid to be produced aredefined as follows:

The conversion (%) of an olefin or an α,β-unsaturatedaldehyde=(B/A)×100;

The selectivity (%) to an α,β-unsaturated aldehyde=(C/B)×100;

The selectivity (%) to an α,β-unsaturated carboxylic acid=(D/B)×100;

The selectivity (%) to a polymer/oligomer=(E/B)×100;

The yield (%) of an α,β-unsaturated carboxylic acid=(D/A)×100; and

The productivity (g/(g·h)) of an α,β-unsaturated carboxylic acid=F/(G×H)

In the above formulae, A represents mol number of an olefin or anα,β-unsaturated aldehyde supplied; B represents mol number of an olefinor an α,β-unsaturated aldehyde reacted; C represents mol number of anα,βunsaturated aldehyde produced; D represents mol number of anα,βunsaturated carboxylic acid produced; E represents reduced mol numberof a polymer and oligomer produced based on an olefin or anα,β-unsaturated aldehyde, which is calculated by dividing total weight(unit: g) of a polymer and oligomer produced by molecular weight of anolefin or an α,β-unsaturated aldehyde supplied; F represents weight(unit: g) of an α,β-unsaturated carboxylic acid produced; G representsweight (unit: g) of a metal contained in a catalyst used; and Hrepresents reaction time (unit: hour). Further, in the case ofliquid-phase oxidation reaction of an α,β-unsaturated aldehyde, C/B is0.

(Measurements of Physical Properties of a Carrier)

Measurements of pore volume and pore size distribution of a carrier werecarried out with fixed volume method based on nitrogen gas adsorptionmethod by using Surface Area and Porosimetry Analyzer, TriStar 3000(trade name), manufactured by Micromeritics Instrument Corporation. Thepore size measurable by this method is in the range of about from 1 to100 nm, and all the pore volumes and pore size distributions describedin the present invention were calculated based on changes in thequantity of nitrogen adsorbed (adsorption isotherm) according to thedirection of raising the relative pressure (adsorption equilibratedpressure/saturated vapor pressure).

In the above measurement, total pore volume per unit weight of a carrierand BET specific surface area were measured by using t-plot method.Further, pore volume of pores having a pore size of from 2 nm through 50nm (mesopore) was calculated by using BJH method, and a proportion ofthe mesopore to the total pore volume was calculated.

(Average Particle Diameter of Palladium in a Palladium-ContainingSupported Catalyst)

Average particle diameter of palladium in a palladium-containingsupported catalyst was measured with transmission electron microscope,and concretely, calculated as follows. Print out an image oftransmission electron microscope with the same magnification as that ofthe observation, and randomly sample 50 points of the palladium regionsin the field of view and measure particle diameter of each palladiumregion; measure the particle diameter by assuming its shape to becircular because the shape of the palladium region is almost circular;and carry out these operations with 3 fields of view and average themeasured values to obtain an average particle diameter.

Example 1

(Preparation of Catalyst)

To 55 parts of 88% by weight n-valeric acid aqueous solution, 1 part ofpalladium acetate (manufactured by N.E.CHEMCAT Corporation) wasdissolved. The resultant solution was introduced into an autoclave towhich 5 parts of activated carbon made from synthesized raw material(total pore volume: 0.64 cc/g; BET specific surface area: 1,313 m²/g;proportion of the pore volume of mesopore having a pore size of from 2nm through 50 nm to the total pore volume: 7.8%) manufactured by KURARAYCHEMICAL Co., Ltd. was added. The resultant mixture was stirred. Afterpropylene was introduced to the system pressure of 0.5 MPa, theresultant system was heated to 50° C. in 30 minutes and reduced for 30minutes. After the reduction, palladium supported catalyst thus obtainedwas filtered, washed and replaced by 88% by weight acetic acid aqueoussolution, and filtered. Finally, palladium-containing supportedcatalyst, the supported ratio of which was 10% by weight was obtained.

(Evaluation of Reaction)

To the autoclave, 135 parts of 88% by weight acetic acid aqueoussolution containing 200 ppm of para-metoxyphenol (polymerizationinhibitor) was introduced, and 5.5 parts of the above-mentionedpalladium-containing supported catalyst, the supported ratio of whichwas 10% by weight was added. Further, 4.5 parts of methacrolein wasadded to it and the reactor was shut tight. Then, the temperature wasraised to 90° C. while stirring. Air was introduced to the systempressure of 3.2 MPa and oxidation reaction of methacrolein was carriedout for 20 minutes. The amount of molecular oxygen used in the oxidationreaction was 0.76 mol to 1 mol of methacrolein. After the reaction wasfinished, the autoclave was cooled to around the room temperature andthe reaction liquid was taken out. The reaction liquid from which thecatalyst had been separated was analyzed with gas chromatography.

As the result, the conversion of methacrolein was 84.0%, the selectivityto methacrylic acid was 83.2% and the productivity of methacrylic acidwas 23.1 g/(g·h).

Example 2

The preparation of the catalyst and the evaluation of the reaction werecarried out in the same manner as in Example 1 except that coconut shellactivated carbon (total pore volume: 0.49 cc/g; BET specific surfacearea: 988 m²/g; proportion of the pore volume of mesopore having a poresize of from 2 nm through 50 nm to the total pore volume: 10%)manufactured by KURARAY CHEMICAL Co., Ltd. was used as a carrier.

As the result, the conversion of methacrolein was 89.7%, the selectivityto methacrylic acid was 84.7% and the productivity of methacrylic acidwas 25.2 g/(g·h).

Example 3

The preparation of the catalyst and the evaluation of the reaction werecarried out in the same manner as in Example 1 except that coal-derivedactivated carbon (total pore volume: 0.46 cc/g; BET specific surfacearea: 753 m²/g; proportion of the pore volume of mesopore having a poresize of from 2 nm through 50 nm to the total pore volume: 33%)manufactured by DAINEN CO., LTD. was used as a carrier.

As the result, the conversion of methacrolein was 84.4%, the selectivityto methacrylic acid was 80.1% and the productivity of methacrylic acidwas 22.4 g/(g·h).

Example 4

The preparation of the catalyst and the evaluation of the reaction werecarried out in the same manner as in Example 1 except that activatedcarbon made from synthesized raw material (total pore volume: 0.75 cc/g;BET specific surface area: 1,613 m²/g; proportion of the pore volume ofmesopore having a pore size of from 2 nm through 50 nm to the total porevolume: 4.0%) manufactured by KURARAY CHEMICAL Co., Ltd. was used as acarrier.

As the result, the conversion of methacrolein was 78.3%, the selectivityto methacrylic acid was 80.1% and the productivity of methacrylic acidwas 20.8 g/(g·h).

Example 5

The preparation of the catalyst and the evaluation of the reaction werecarried out in the same manner as in Example 1 except that coal-derivedactivated carbon (total pore volume: 0.92 cc/g; BET specific surfacearea: 1,345 m²/g; proportion of the pore volume of mesopore having apore size of from 2 nm through 50 nm to the total pore volume: 52%)manufactured by DAINEN CO., LTD. was used as a carrier and reaction timewas 11 minutes.

As the result, the conversion of methacrolein was 90.3%, the selectivityto methacrylic acid was 77.3% and the productivity of methacrylic acidwas 42.1 g/(g·h).

Example 6

The preparation of the catalyst and the evaluation of the reaction werecarried out in the same manner as in Example 1 except that activatedcarbon made from synthesized raw material (total pore volume: 1.27 cc/g;BET specific surface area: 2,587 m²/g; proportion of the pore volume ofmesopore having a pore size of from 2 nm through 50 nm to the total porevolume: 26%) manufactured by KURARAY CHEMICAL Co., Ltd. was used as acarrier and reaction time was 11 minutes.

As the result, the conversion of methacrolein was 89.5%, the selectivityto methacrylic acid was 78.3% and the productivity of methacrylic acidwas 42.3 g/(g·h).

Example 7

The preparation of the catalyst and the evaluation of the reaction werecarried out in the same manner as in Example 1 except thatcharcoal-derived activated carbon (total pore volume: 1.30 cc/g; BETspecific surface area: 1,692 m²/g; proportion of the pore volume ofmesopore having a pore size of from 2 nm through 50 nm to the total porevolume: 58%) manufactured by Norit Corporate was used as a carrier andreaction time was 15 minutes.

As the result, the conversion of methacrolein was 86.9%, the selectivityto methacrylic acid was 76.2% and the productivity of methacrylic acidwas 29.3 g/(g·h).

Comparative Example 1

The preparation of the catalyst and the evaluation of the reaction werecarried out in the same manner as in Example 1 except that coal-derivedactivated carbon (total pore volume: 1.61 cc/g; BET specific area: 3,174m²/g; proportion of the pore volume of mesopore having a pore size offrom 2 nm through 50 nm to the total pore volume: 35%) manufactured byTHE KANSAI COKE AND CHEMICALS CO., LTD. was used as a carrier.

As the result, the conversion of methacrolein was 35.0%, the selectivityto methacrylic acid was 24.3% and the productivity of methacrylic acidwas 2.8 g/(g·h).

Comparative Example 2

The preparation of the catalyst and the evaluation of the reaction werecarried out in the same manner as in Example 1 except that wood-derivedactivated carbon (total pore volume: 1.61 cc/g; BET specific surfacearea: 1,680 m²/g; proportion of the pore volume of mesopore having apore size of from 2 nm through 50 nm to the total pore volume: 68%)manufactured by Norit Corporate was used as a carrier.

As the result, the conversion of methacrolein was 83.1%, the selectivityto methacrylic acid was 54.5% and the productivity of methacrylic acidwas 15.0 g/(g·h).

Comparative Example 3

The preparation of the catalyst and the evaluation of the reaction werecarried out in the same manner as in Example 1 except that activatedcarbon made from synthesized raw material (total pore volume: 0.37 cc/g;BET specific surface area: 690 m²/g; proportion of the pore volume ofmesopore having a pore size of from 2 nm through 50 nm to the total porevolume: 2.7%) manufactured by KURARAY CHEMICAL Co., Ltd. was used as acarrier.

As the result, the conversion of methacrolein was 50.5%, the selectivityto methacryli; acid was 65.2% and the productivity of methacrylic acidwas 10.9 g/(g·h).

A summery of the physical properties of the carriers used and theresults of the reaction in Examples 1 to 7 and Comparative Examples 1 to3 are shown in Table 1. In Examples 1 to 7 where a carrier with a totalpore volume of 0.40 to 1.50 cc/g was used, it was found that theselectivity to methacrylic acid and the productivity of methacrylic acidwere good. Further, in Examples 1 to 4 where a carrier with a smallertotal pore volume was used, it was found that the selectivity tomethacrylic acid was particularly good. Moreover, in Examples 5 to 7where a carrier with a larger total pore volume was used, it was foundthat the productivity of methacrylic acid was particularly good. TABLE 1Physical properties of carrier Proportion of Total pore size of ReactionSelectivity to Selectivity to Productivity of pore volume 2 to 50 nmtime methacrolein methacrylic acid methacrylic acid (cc/g) (%) (min) (%)(%) (g/(g · h)) Ex. 1 0.64 7.8 20 84.0 83.2 23.1 Ex. 2 0.49 10 20 89.784.7 25.2 Ex. 3 0.46 33 20 84.4 80.1 22.4 Ex. 4 0.75 4.0 20 78.3 80.120.8 Ex. 5 0.92 52 11 90.3 77.3 42.1 Ex. 6 1.27 26 11 89.5 78.3 42.3 Ex.7 1.30 58 15 86.9 76.2 29.3 Comp. 1.61 35 20 35.0 24.3 2.8 Ex. 1 Comp.1.61 68 20 83.1 54.5 15.0 Ex. 2 Comp. 0.37 2.7 20 50.5 65.2 10.9 Ex. 3

Example 8

(Preparation of Catalyst)

To 20 parts of acetic acid, 1.05 parts of palladium acetate(manufactured by N. E. CHEMCAT Corporation) was dissolved. The resultantsolution was added to 10 parts of silica carrier (total pore volume:0.68 cc/g; BET specific surface area: 450 m²/g; proportion of the porevolume of mesopore having a pore size of from 2 nm through 50 nm to thetotal pore volume: 100%) and shaken. The resultant mixture wasevaporated. Then it was calcined at 450° C. in the air for 3 hours. Tothe catalyst precursor thus obtained, 13 parts of 37% by weightformaldehyde aqueous solution was added. The resultant mixture washeated to 70° C., and kept for 2 hours while stirring, filtered underreduced pressure, and the filter cake was washed and filtered by waterand 75% by weight t-butanol aqueous solution. Finally,palladium-containing supported catalyst, the supported ratio of whichwas 5% by weight, was obtained.

(Evaluation of Reaction)

To an autoclave, the whole catalyst (10.5 parts) obtained in theabove-mentioned method, 100 parts of 75% by weight t-butanol aqueoussolution as a reaction solvent and 0.02 part of p-metoxyphenol wereintroduced, and the autoclave was shut tight. Then, 2.75 parts ofisobutylene was introduced to it and stirring of the system was carriedout (number of revolutions: 1,000 rpm) and the temperature of the systemwas raised to 90° C. When the temperature reached 90° C., nitrogen wasintroduced into the autoclave to the internal pressure of 2.3 MPa, andthe compressed air was introduced into the autoclave to the internalpressure of 4.6 MPa. Every time when the internal pressure dropped by0.1 MPa with the progress of the reaction, oxygen gas was introduced tocompensate this internal pressure of 0.1 MPa, and this operation wasrepeated 10 times. After the 10th introduction of oxygen, when theinternal pressure dropped by 0.1 MPa, the reaction was finished. At thistime, the reaction time was 56 minutes. In the oxidation reaction, 3.48mols of molecular oxygen to 1 mol of isobutylene was used.

After the reaction was finished, inside of the autoclave was cooled inice bath. A gas sampling bag was attached to a gas outlet port of theautoclave and the product gas was recovered by opening the gas outletport and reducing the internal pressure of the reactor. The reactionliquid containing the catalyst was taken out from the autoclave, and thecatalyst was separated by using membrane filter to recover the reactionsolution. The recovered reaction solution and the collected gas wereanalyzed with gas chromatography and the conversion and the selectivitywere calculated.

As the result, the conversion of isobutylene was 90.7%, the selectivityto methacrolein was 28.2%, the selectivity to methacrylic acid was 28.6%and the productivity of methacrylic acid was 2.2 g/(g·h).

Example 9

The same method as in Example 8 was carried out except that a carrier tobe used was changed to Y-type zeolite (total pore volume: 0.50 cc/g; BETspecific surface area: 629 m²/g; proportion of the pore volume ofmesopore having a pore size of from 2 nm through 50 nm to the total porevolume is 42%), silica/alumina (SiO_(2/Al) ₂O₃) mol ratio of which was200, to obtain Y-type zeolite supported palladium-containing catalyst inwhich palladium metal was supported.

The reaction was carried out by using the catalyst obtained in the abovein the same method as in Example 8 except that the reaction time was 38minutes. As the result, the conversion of isobutylene was 75.2%, theselectivity to methacrolein was 49.9%, the selectivity to methacrylicacid was 19.0% and the productivity of methacrylic acid was 1.9 g/(g·h).

Comparative Example 4

The same method as in Example 8 was carried out except that a carrier tobe used was changed to H-ZSM-5-type zeolite (total pore volume: 0.20cc/g; BET specific surface area: 343 m²/g; proportion of the pore volumeof mesopore with a pore size of 2 nm to 50 nm to the total pore volumeis 29%), silica/alumina (SiO₂/Al₂O₃) mol ratio of which was 485, toobtain H-ZSM-5-type zeolite supported palladium-containing catalyst inwhich palladium metal was supported.

The reaction was carried out by using the catalyst obtained in the abovein the same method as in Example 8 except that the reaction time was 107minutes. As the result, the conversion of isobutylene was 67.4%, theselectivity to methacrolein was 59.1%, the selctivity to methacrylicacid was 15.4% and the productivity of methacrylic acid was 0.5 g/(g·h).

A summery of the physical properties of the carriers used and theresults of the reaction in Examples 8 and 9 and Comparative Example 4are shown in Table 2. In Examples 8 and 9 where a carrier with a totalpore volume of 0.40 to 1.50 cc/g was used, it was found that theselectivity to methacrylic acid and the productivity of methacrylic acidwere good. TABLE 2 Physical properties of carrier Proportion of Totalpore size of Reaction Selectivity to Selectivity to Selectivity toProductivity of pore volume 2 to 50 nm time isobutylene methacroleinmethacrylic acid methacrylic acid (cc/g) (%) (min) (%) (%) (%) (g/(g ·h)) Ex. 8 0.68 100 56 90.7 28.2 28.6 2.2 Ex. 9 0.50 42 38 75.2 49.9 19.01.9 Comp. 0.20 29 107 67.4 59.1 15.4 0.5 Ex. 4

Example 10

(Preparation of Catalyst)

To 60 parts of 88% by weight n-valeric acid aqueous solution, 1.16 partsof palladium acetate was added and stirred under heating at 80° C. for 1hour and dissolved. The resultant solution was introduced into anautoclave to which 5.4 parts of activated carbon made from raw coal(total pore volume: 0.43 cc/g; BET specific surface area: 840 m²/g;proportion of the pore volume of mesopore having a pore size of from 2nm through 50 nm to the total pore volume is 26%) was added. The systemwas stirred at a number of revolutions of 400 rpm, and inside of theautoclave was replaced by nitrogen by introducing and dischargingnitrogen gas several times. Propylene gas was introduced into it to thepressure of 0.5 MPa and the resultant system was heated to 50° C.(reducing temperature) and kept at the same temperature for 1 hour(reducing time). After the reaction was finished, the system was cooledto 20° C., and the gas inside the autoclave was discharged and theautoclave was opened. The suspension was filtered andpalladium-containing supported catalyst, the supported ratio of whichwas 10% by weight (the weight of palladium to the weight of carrier),was obtained.

The average particle diameter of palladium in the palladium-containingsupported catalyst thus obtained was 1.5 nm (magnification ofobservation by transmission electron microscope: 1,000,000 fold).

(Evaluation of Reaction)

To the autoclave equipped with stirring device, 69 parts of 88% byweight acetic acid aqueous solution containing 200 ppm of p-metoxyphenoland 3 parts of the above-mentioned palladium-containing supportedcatalyst were introduced. Further, 2.5 parts of methacrolein was added.The autoclave was shut tight and stirring was carried out at a number ofrevolutions of 820 rpm, and the temperature was raised to 90° C. byheater. When the temperature reached 90° C., air was introduced into theautoclave to the internal pressure of 3.2 MPa, and the system wasmaintained in the same state for 20 minutes (reaction time). The amountof molecular oxygen used in the oxidation reaction was 0.77 mol to 1 molof methacrolein. After the reaction was finished, the system was cooledto 20° C. To the gas outlet port of the autoclave, an absorption tubewith cooled water inside and a gas sampling bag were attached in thisorder. The product gas was recovered by opening the gas outlet port andreducing the internal pressure of the reactor. The reaction liquid wastransferred to a centrifuge tube and the catalyst was precipitated bycentrifugation. The supernatant liquid was recovered by passing throughmembrane filter made of PTFE (pore size: 0.5 μm.

As the result, the conversion of methacrolein was 93.6%, the selectivityto methacrylic acid was 79.9%, the selectivity to a polymer/oligomer was8.5% and the yield of methacrylic acid was 74.8%.

Example 11

The preparation of the catalyst was carried out in the same manner as inExample 10 except that an activated carbon made from raw coconut shell(total pore volume: 0.49 cc/g; BET specific surface area: 988 m²/g;proportion of the pore volume of mesopore having a pore size of from 2nm through 50 nm to the total pore volume: 10%) was used as a carrier.The average particle diameter of palladium in the palladium-containingsupported catalyst thus obtained (the supported ratio of which was 10%by weight) was 2.6 nm (magnification of observation by transmissionelectron microscope: 300,000 fold).

The evaluation of the reaction was carried out in the same manner as inExample 10, and as the result, the conversion of methacrolein was 89.7%,the selectivity to methacrylic acid was 84.7%, the selectivity to apolymer/oligomer was 4.3% and the yield of methacrylic acid was 76.0%.

Comparative Example 5

The preparation of the catalyst was carried out in the same manner as inExample 10 except that 96% by weight of acetic acid aqueous solution wasused as a solvent for preparation of catalyst. The average particlediameter of palladium in the palladium-containing supported catalystthus obtained (the supported ratio of which was 10% by weight) was 8.4nm (magnification of observation by transmission electron microscope:300,000 fold).

The evaluation of the reaction was carried out in the same manner as inExample 10, and as the result, the conversion of methacrolein was 46.4%,the selectivity to methacrylic acid was 71.5%, the selectivity to apolymer/oligomer was 15.4% and the yield of methacrylic acid was 33.2%.

Comparative Example 6

The preparation of the catalyst was carried out in the same manner as inExample 10 except that n-valeric acid was used as a solvent forpreparation of catalyst. The average particle diameter of palladium inthe palladium-containing supported catalyst thus obtained (the supportedratio of which was 10% by weight) was 10.1 nm (magnification ofobservation by transmission electron microscope: 300,000 fold).

The evaluation of the reaction was carried out in the same manner as inExample 10, and as the result, the conversion of methacrolein was 45.4%,the selectivity to methacrylic acid was 65.2%, the selectivity to apolymer/oligomer was 21.3% and the yield of methacrylic acid was 30.0%.

Comparative Example 7

The preparation of the catalyst was carried out in the same manner as inExample 10 except that 0.11 parts of palladium acetate was used,reducing temperature was 25° C., and reducing time was 18 hours. Theaverage particle diameter of palladium in the palladium-containingsupported catalyst thus obtained (the supported ratio of which was 10%by weight) was 0.8 nm (magnification of observation by transmissionelectron microscope: 1,000,000 fold).

The evaluation of the reaction was carried out in the same manner as inExample 10 except that reaction time of methacrolein was 3 hours, and asthe result, the conversion of methacrolein was 42.5%, the selectivity tomethacrylic acid was 59.8%, the selectivity to a polymerloligomer was29.6% and the yield of methacrylic acid was 25.4%

A summery of the average particle diameter of palladium in the catalystsused and the results of the reaction in Examples 10 and 11 andComparative Examples 5 to 7 are shown in Table 3. In Examples 10 and 11where a catalyst with an average particle diameter of palladium of 1 to8 nm was used, it was found that the selectivity to methacrylic acid washigh. TABLE 3 Average particle diameter Conversion of Selectivity toSelectivity to Yield of of palladium methacrolein methacrylic acidpolymer/oligomer methacrylic acid (nm) (%) (%) (%) (%) Ex. 10 1.5 93.679.9 8.5 74.8 Ex. 11 2.6 89.7 84.7 4.3 76.0 Comp. 8.4 46.4 71.5 15.433.2 Ex. 5 Comp. 10.1 45.4 65.2 21.3 30.0 Ex. 6 Comp. 0.8 42.5 59.8 29.625.4 Ex. 7

As mentioned above, by using the catalyst of the present invention, anα,β-unsaturated carboxylic acid can be produced through liquid-phaseoxidation of an olefin or an α,β-unsaturated aldehyde in good reactionperformance.

1. A catalyst for producing an α,β-unsaturated carboxylic acid through liquid-phase oxidation of an olefin or an α,β-unsaturated aldehyde, comprising a metal supported on a carrier with a total pore volume of 0.40 to 1.50 cc/g as measured by nitrogen gas adsorption method.
 2. The catalyst for producing an α,β-unsaturated carboxylic acid according to claim 1, wherein the total pore volume of the carrier as measured by nitrogen gas adsorption method is 0.40 to 0.80 cc/g.
 3. The catalyst for producing an α,β-unsaturated carboxylic acid according to claim 2, wherein a proportion of the pore volume of the mesopore having a pore size of from 2 nm through 50 nm of the carrier as measured by nitrogen gas adsorption method to the total pore volume of the carrier is 40% or less.
 4. The catalyst for producing an α,β-unsaturated carboxylic acid according to claim 1, wherein the total pore volume of the carrier as measured by nitrogen gas adsorption method is 0.80 to 1.50 cc/g.
 5. The catalyst for producing an α,β-unsaturated carboxylic acid according to claim 4, wherein a proportion of the pore volume of the mesopore having a pore size of from 2 nm through 50 nm of the carrier as measured by nitrogen gas adsorption method to the total pore volume of the carrier is 10% or less.
 6. A catalyst for producing an α,β-unsaturated carboxylic acid through liquid-phase oxidation of an olefin or an α,β-unsaturated aldehyde, comprising palladium with an average particle diameter in the range of 1 to 8 nm supported on a carrier.
 7. A method for producing the catalyst for producing an α,β-unsaturated carboxylic acid according to claim 1, wherein a metal compound is reduced by a reducing agent in the presence of the carrier.
 8. A method for producing the catalyst for producing an α,β-unsaturated carboxylic acid according to claim 6, comprising reducing a palladium compound by a reducing agent in the presence of the carrier.
 9. A method for producing an α,β-unsaturated carboxylic acid through liquid-phase oxidation of an olefin or an α,β-unsaturated aldehyde with molecular oxygen in the presence of the catalyst for producing an α,β-unsaturated carboxylic acid according to claim
 1. 10. A method for producing the catalyst for producing an α,β-unsaturated carboxylic acid according to claim 2, comprising reducing a metal compound by a reducing agent in the presence of the carrier.
 11. A method for producing the catalyst for producing an α,β-unsaturated carboxylic acid according to claim 3, comprising reducing a metal compound by a reducing agent in the presence of the carrier.
 12. A method for producing the catalyst for producing an α,β-unsaturated carboxylic acid according to claim 4, comprising reducing a metal compound by a reducing agent in the presence of the carrier.
 13. A method for producing the catalyst for producing an α,β-unsaturated carboxylic acid according to claim 5, comprising reducing a metal compound is reduced by a reducing agent in the presence of the carrier.
 14. A method for producing an α,β-unsaturated carboxylic acid through liquid-phase oxidation of an olefin or an α,β-unsaturated aldehyde with molecular oxygen in the presence of the catalyst for producing an (α,β-unsaturated carboxylic acid according to claim
 2. 15. A method for producing an α,β-unsaturated carboxylic acid through liquid-phase oxidation of an olefin or an α,β-unsaturated aldehyde with molecular oxygen in the presence of the catalyst for producing an α,β-unsaturated carboxylic acid according to claim
 3. 16. A method for producing an α,β-unsaturated carboxylic acid through liquid-phase oxidation of an olefin or an (α,β-unsaturated aldehyde with molecular oxygen in the presence of the catalyst for producing an α,β-unsaturated carboxylic acid according to claim
 4. 17. A method for producing an α,β-unsaturated carboxylic acid through liquid-phase oxidation of an olefin or an (α,β-unsaturated aldehyde with molecular oxygen in the presence of the catalyst for producing an α,β-unsaturated carboxylic acid according to claim
 5. 18. A method for producing an α,β-unsaturated carboxylic acid through liquid-phase oxidation of an olefin or an α,β-unsaturated aldehyde with molecular oxygen in the presence of the catalyst for producing an (α,β-unsaturated carboxylic acid according to claim
 6. 